Buying two new fish will they be compatible?

[oompala]

I have a 90 gal FOWLR tank and currently have the following in the tank:
Vlamingi Tang (has been in tank for about 2 yrs)
Yellow Tang (has been in tank for about 4 mos)
(2) Clownfish
Chocolate Chip Starfish
Brittle Starfish
My LFS has a good price on Flame Angel and Regal Tang. I would like to get both, but want to make sure they will get along with what I already have or each other (currently they are in separate tanks at LFS). Plus i'm not sure if the Yellow Tang and Regal Tang will get along?
If the Regal Tang is not a good idea, what would be a good choice for a blue colored fish?

 

[luvmyreef]

Well, I can tell you from experience that my yellow tang has killed an angel and another tang..
The only way I knowto "test" him is to hold a pic against the tank of the fish I want and see his reaction.. He flogs everything except a clown pic.
they can get so territorial...